Servants/prisoners....explain? SPOILERS

[Vael]

Alright, well there are the men who wandered the forest that were already monster-like beings. The notes provided in the game details them as horrid-looking and whatnot. They worked for Alexander to provide that one type of essence he needed to

Spoiler below!

fuel the machine he used at the end of the game

Then the Shadow followed Daniel due to the Orb and possessed Brennenburg so Daniel had two enemies to face: the monsters and the Shadow. I'm not sure how Alexander controls the Gatherers (monsters) in Brennenburg, but it's possible they just follow his orders because he bossed them around before Daniel was even known by the Baron.

I'm not 100% sure about it all, so if you have any idea or actual answers then please correct me.